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Old 09-29-2018, 02:30 PM   #1
71chevswb
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How to optimize a RCSB for gas mileage

In the market for a 99-07 chevy/gmc single cab short bed (rcsb) 2wd..... I'm looking for one with a 5.3l .... I've always wanted one. It will be a commuter vehicle for me. Driving 55-70 mph about 80-90 miles a day for 3 or 4 days a week.


My question is, what kind of gas mileage can I expect? I would ideally like to push it to 22 mpg. I know this is a bit of a stretch. What speed, air dams, tonneau cover, etc... can I add to achieve this? Will a 4/6 drop help at all? I plan to add a 4/6 drop either way. What wheel/tire size will work best? Will a 4.3 or 4.8 be any better? My thought process is that a bigger motor wont have to work as hard.


Any thoughts or suggestions are appreciated. I know this is not the best "commuter" vehicle but I'm currently driving a v6 tacoma 4x4 getting 16-18 mpg.
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Old 10-02-2018, 06:02 PM   #2
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Re: How to optimize a RCSB for gas mileage

Doesn't matter if it isn't working as hard, your still turning a certain number of RPM's and moving air threw the engine that needs fuel added. The 4.8 vs 5.3 seems to work out like your thinking, but the v6 will get better mileage.
As for mods to help, everything you listed helps. Bed cover, lower the truck, keep small rims on it [the lighter weight the better]. Make sure the factory air dam under the front bumper is there.
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Old 10-02-2018, 08:24 PM   #3
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Re: How to optimize a RCSB for gas mileage

4.3L/5 speed manual is your huckleberry if you can find one. It has plenty of power and is efficient in the right package. Custom tune, smaller/lighter wheels and low rolling resistance tires. Synthetic fluids throughout. You could expect about 18mpg combined, 19 tops if you drive like an old lady. 22 combined is probably not going to happen.
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Old 10-11-2018, 06:38 PM   #4
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Re: How to optimize a RCSB for gas mileage

My 06 rcsb had the 4.3/Auto and when it had the 17" steel wheels it got 17mpg. The truck was lowered 5/7 K&N cold air intake and magnaflow cat back exhaust. I would get the 5.3 like you mentioned.

Here is a picture:
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Old 10-21-2019, 10:28 PM   #5
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Re: How to optimize a RCSB for gas mileage

Would going to 3.08 gears help much?

The new ecotec motors with the 6l80e transmissions really perform well both power and economy wise. Seems as if 3.08s would act similar
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Old 10-22-2019, 07:19 AM   #6
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Re: How to optimize a RCSB for gas mileage

I have owned several 4.3V6 and a 4.8 V8 ones. With today's ethenal gas, seeing 20 is possible, but a little tuff. I loved them as DDs. For best gas mileage, keep the skinny factory wheels and tires. I had 8" wheels and 265/70 tires. I liked the ride and handling, but it will eat a bit into the MPG. AS mentioned a 4.3 V6 and manual will give you the bext chance of MPG. Most trucks came with a 3:42 rear gear with the V^ till aroun 2005, then they went to 3.23 gears. As far as automatics, my 4.8 V* one ended up with the best MPG average consistently.

My 92 V6 w 5 speed average 21 MPG Hwy (for whatever reason in Colorado Springs/Denver I averaged 23-24)
2002 V6, 3.42 gears 20 MPG Hwy
2007 4.8 V8, 3.23 gears 21-22MPG
2006 V6 3.23 gears 21 MPG

Now Highway for me is 70-80, mostly flat land.

I miss my RCSB truck. Love them as a daily, and they are getting harder and harder to find.
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Old 10-22-2019, 09:22 AM   #7
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Re: How to optimize a RCSB for gas mileage

Thanks for the info from your personal experience!


I'm pretty dead set on a 5.3L. I know they are getting tougher to find, hence why I'm still looking. With that said, I'd like to optimize one with the 5.3. I know getting a 5.3 is counter intuitive when it comes to wanting good gas mileage but we have owned several vehicles with the 5.3 and can't imagine going with another motor. Plus they typically come with nicer interiors than the standard 4.3L work truck.

The desire for decent fuel economy is a shorter term desire as I travel often right now. In years to come a cammed 5.3 or 6.0 might be in store for this project.
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Old 10-22-2019, 04:07 PM   #8
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Re: How to optimize a RCSB for gas mileage

If you really want mpg. Take a look at the 14+ Silverados with the V6.

I have a 18 crew cab with a 2/4 drop, and usually average right around 26 highway at 66-70 mph. Goes slower doesn't help, and faster it drops quick. Trailing a semi helps alot, but I rarely get to cruise behind one.

If I cruise from LA to Lancater, and back. Ac on or off doesn't matter much. Even with the hill going there I get right around 25 round trip. I have hauled a 7500 trailer over the mountains around lake tahoe, and it did amazing.

As for the early model your looking at. I liked my 4.8 in the new 07 model. 21-22 highway at 70-75. It had 3.23's when I got it, and I swapped to 4.33's. The hwy mpg stayed the same, but the city mpg went up alot. It used to get something like 13/22, and after the gear swap it got like 17/22.

Tonneo covers help alot of you have a tool box or keep stuff in the bed. As this messes up air flow. So if you keep the bed clean they do effectively nothing. Also consider a roll up soft tonneau as they as very flexible since it they roll up.

When I got my 07 I put in a tool box and my mpg went from 21 to 17 hwy. I got a tool box soft tonneau, and it went back to 22. Not enough to justify it by itself.
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Old 10-22-2019, 09:06 PM   #9
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Re: How to optimize a RCSB for gas mileage

Quote:
Originally Posted by Ziegelsteinfaust View Post
If you really want mpg. Take a look at the 14+ Silverados with the V6.

I have a 18 crew cab with a 2/4 drop, and usually average right around 26 highway at 66-70 mph. Goes slower doesn't help, and faster it drops quick. Trailing a semi helps alot, but I rarely get to cruise behind one.

If I cruise from LA to Lancater, and back. Ac on or off doesn't matter much. Even with the hill going there I get right around 25 round trip. I have hauled a 7500 trailer over the mountains around lake tahoe, and it did amazing.

As for the early model your looking at. I liked my 4.8 in the new 07 model. 21-22 highway at 70-75. It had 3.23's when I got it, and I swapped to 4.33's. The hwy mpg stayed the same, but the city mpg went up alot. It used to get something like 13/22, and after the gear swap it got like 17/22.

Tonneo covers help alot of you have a tool box or keep stuff in the bed. As this messes up air flow. So if you keep the bed clean they do effectively nothing. Also consider a roll up soft tonneau as they as very flexible since it they roll up.

When I got my 07 I put in a tool box and my mpg went from 21 to 17 hwy. I got a tool box soft tonneau, and it went back to 22. Not enough to justify it by itself.

I wish a 5.3/6l80e combo was in budget. Especially those new ecotec 5.3s... but that is beyond my budget for a daily!
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Old 10-24-2019, 09:42 PM   #10
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Re: How to optimize a RCSB for gas mileage

Had the RCSB 4.3 5speed for 7 years.
245-70 tires on the steel wheels, 3.23 rear.
15-16 mpg in town and about 21 highway.
(a mile or two less in the winter with the crappy winter gas)
Unless I drove like an idiot....
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Old 10-29-2019, 10:59 AM   #11
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Re: How to optimize a RCSB for gas mileage

I bought my buddies 2005 1/2 ton SWB, looks exactly like post 4
He was looking to tow with it. It has the tow package 5.3 automatic trans,3.73 gears. THe tow package rides a little stiff, doesn't bother me. He blessed me by selling it to me shortly before he pass, so I will own it, till the cows come home.
It gets 20 MPG, I've heard of the standard suspension pickups that have the 3.23 gear get 22-24 MPG, with the 5.3

He had a 2000 model standard pickup, 2WD, SWB with the V6, it got 20 MPG. THe v6 wasn't gutless, but man, the 5.3 has great power. I wouldn't buy anything but a 5.3
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Old 11-07-2019, 12:15 AM   #12
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Re: How to optimize a RCSB for gas mileage

I picked up mine a little over a year ago a 01 5.3 has 183K+ miles I got a little over 19 MPG @ close to 80MPH (with the JD in the back 200 of the 400 miles)
Since then I had a misfire code so I replaced all the coil packs It seemed to pick up some MPG but I have not checked it yet
And yes it is a fun little daily driver it was worth the wait
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